Reson 8101ER multibeam Data were collected from
15 Jan - 6 Feb aboard NOAA Survey Launch Acoustic
Habitat Investigator (AHI) at Johnston Island, Howland
Island, and Baker Island in the Central Pacific during
cruise AHI-06-01. These multibeam data were collected
using SAIC ISS-2000 software in the Generic Sensor Format
and processed using SABER editing software. Sound velocity
corrections from a Seabird SBE19 CTD sensor and motion
corrections from a POS-MV vertical reference were applied
to the data in real time. Predicted tides were applied
to the data in real time: for Johnston
Island predicted tides from the NOS CO-OPS web site were
used; for Baker and Howland Islands predicted tides based
upon the Honolulu tide station (1612340) with a time corrector
of 3 hrs 48 min and a range ratio of 3.91.

Horizontal accuracy is 20m (no differential GPS correctors
applied), vertical accuracy is depth dependent (~1% of
water depth), WGS84 datum. These data are not to be used
for navigation. Depths mapped range from ~10 - 300 m. The
AHI was deployed from the NOAA Ship Hi'ialakai and
concurrent mapping was done using Simrad EM300 and EM3002D
sonars aboard the ship; metadata for HI- 06-01 are
submitted separately.

R/V AHI Lever Arm Distances and Alignment Offsets: The R/V
AHI Reference Point (RP) is defined to be the intersection
of the vessel's centerline, the cabin deck and the bulkhead
immediately aft of the transducer. This is marked by a
punch in the deck weld at that location. Positive X means
the point is forward of the RP, positive Y means the point
is to starboard of the RP, positive Z means the point is
below the RP. The loaded waterline is defined as the
intersection of the vessel's performance wing with the hull
at the transom.

The data were collected in support of Coral Reef
Conservation Program goals to map all shallow (0-30 m)coral
reefs in US Pacific waters and priority moderate (> 30 m)
depth areas by 2009. The data are being used to provide
bathymetric and backscatter data for previously unmapped
areas; in support of ecosystem management requirements for
benthic habitat mapping and location of Essential Fish
Habitat; and to study the geologic features of the area.

Horizontal accuracy is ~20 m as
data were collected using GPS with no differential
corrections. Vertical accuracy of multibeam data is
estimated at 1% of water depth; predicted tidal corrections
were applied.

These data are not to be used for
navigational purposes. NOAA makes no warranty regarding these
data, expressed or implied, nor does the fact of distribution
constitute such a warranty. NOAA cannot assume liability for
any damages caused by any errors or omissions in these data,
nor as a result of the failure of these data to function on a
particular system.